Heretofore, it has been found that the non-linear response of load supporting springs could be corrected by means of a counter-balancing force. This force was introduced by a rotary member having adjustable weights to vary the rotational moment. The rotary member was attached to the load support such that a counter-balancing force was created when the load support deflected. The aforementioned compensating mechanism can be seen in the patent to:
E. C. Karp U.S. Pat. No. 3,308,900 Issued Mar. 14, 1967
Now it must be realized, that the prticular errors which are introduced by the springs are not very substantial. The load bearing springs are for all intended purposes substantially linear. However, the counter-balancing adjustment is made not just to provide an accurate scale, but to provide an extremely accurate scale. Therefore, even slight errors can become significant, where extreme accuracy is concerned.
This previous compensating concept is a very good idea in principle, but it has some serious drawbacks. It is to these drawbacks, that the present invention is addressed. The most serious problem with the prior art system is that the rotary element develops friction by means of its bearings. While bearings can be made almost frictionless, the introduced error (friction) in this particular case cannot be tolerated. This is so, because we are dealing with very minute errors in the first instance. In effect, the previous device took away one error only to introduce another error. What made the situation even worse, was the fact that the introduced error was more critical than the one which was being corrected. As the scale was used, the bearings would degrade, thus adding more and more frictional force to the counter-balance force.
The present invention has as one of its purposes, to provide a corrective system for spring non-linearities which would not have the drawbacks of the prior art devices.